Techniques of constructing variable-size boxes are taught in:
U.S. Pat. No. 6,394,336, to Beneroff et al.;
U.S. Pat. No. 3,598,303, to Folz;
U.S. Pat. No. 4,763,831, to Huang et al.;
U.S. Pat. No. 6,138,901, to Kim et al.;
U.S. Pat. No. 7,070,089, to Kim et al.;
U.S. Pat. No. 6,364,199, to Rose; and
U.S. Pat. No. 4,452,367, to Wein.
In the drawings, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears.